Photodesorption of Water Ices: Highlights from Recent Synchrotron Radiation Studies

UV-X photodesorption of water ices, which is playing a role on the gas-to-ice ratio in a wide range of astrophysical environments, has also been extensively studied in the laboratory. In recent years, the SPICES setup coupled to several beamlines at the SOLEIL facility (France) has allowed the analysis of water photodesorption spectra (PSD) in the vacuum-UV (VUV) and soft X-ray range. Several photodesorption mechanisms have been evidenced: (1) intact water desorption induced by photochemical recombination at the surface of H$_\textbf{2}$O or D$_\textbf{2}$O ices giving rise to a strong isotopic effect (2) indirect desorption in binary ices due to “kick-out” by collision with atoms (H/D) produced by water photodissociation (3) X-ray induced electron desorption (XESD) providing efficient desorption routes for neutrals.